Adding source code for chapter 8

Chapter8/casestudy/casestudy2.py

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+#casestudy2.py: word count application
+import matplotlib.pyplot as plt
+from pyspark.sql import SparkSession
+from wordcloud import WordCloud
+
+spark = SparkSession.builder.master("local[*]")\
+    .appName("word cloud app")\
+    .getOrCreate()
+
+wc_threshold = 1
+wl_threshold = 3
+textRDD = spark.sparkContext.textFile('wordcloud.txt',3)
+flatRDD = textRDD.flatMap(lambda x: x.split(' '))
+wcRDD = flatRDD.map(lambda word: (word, 1)).\
+    reduceByKey(lambda v1, v2: v1 + v2)
+
+# filter out words with fewer than threshold occurrences
+filteredRDD = wcRDD.filter(lambda pair: pair[1] >= wc_threshold)
+filteredRDD2 = filteredRDD.filter(lambda pair:
+                                  len(pair[0]) > wl_threshold)
+
+word_freq = dict(filteredRDD2.collect())
+
+# Create the wordcloud object
+wordcloud = WordCloud(width=480, height=480, margin=0).\
+    generate_from_frequencies(word_freq)
+
+# Display the generated cloud image
+plt.imshow(wordcloud, interpolation='bilinear')
+plt.axis("off")
+plt.margins(x=0, y=0)
+plt.show()